The present invention relates to a tubular packaging casing, in particular to a sausage casing, which is based on cellulose, particularly fiber-reinforced cellulose, and comprises a barrier layer against atmospheric oxygen and steam.
U.S. Pat. No. 4,287,217 discloses a casing comprising fiber-reinforced cellulose hydrate as the substrate material, wherein its inner surface is coated with a continuous film comprising a vinylidene chloride copolymer (PVDC) which is impermeable to water vapor and its outer surface is provided with 0.5 to 0.8 g/m.sup.2 of a coating comprising polyacrylate, which due to a number of interruptions is water-permeable. In the case of this known sausage casing, the inner PVDC layer constitutes the barrier layer, and the permeable acrylate coating applied to the outer surface has the purpose of reducing the sensitivity of the sausage casing to damage due to mechanical shocks, and its undesirable tendency to tear open when being cut through. Because of the barrier layers present on their internal surfaces, sausage casings of this type are employed for the production of cooked and scalded sausages. Application of the polyacrylate dispersion to the outer surface of the casing is effected during the production of the gel-type tubing from viscose, i.e., prior to drying.
The outer surface of the cellulose casing known from U.S. Pat. No. 4,529,634 is also provided with a polyacrylate coating, which has, however, a reduced weight per unit area of less than 0.5 g/m.sup.2. This casing is permeable to water vapor and is intended for use as a sausage casing for air-dried, uncooked sausages of the salami-type. It is not suited for the production of cooked sausages.
Barrier layers based on PVDC have the advantage that virtually no water exudes from the finished sausage during storage, and that even after a relatively long storage period, the casing still surrounds the sausage meat in a tight and creasefree manner. Sausages of the liverwurst-type, whose meat assumes an unattractive appearance when exposed to atmospheric oxygen, remain unchanged, for the PVDC layer also is a barrier towards atmospheric oxygen and prevents the latter from penetrating into the sausage meat. For example, a fiber-reinforced cellulose casing with a 10 to 12 .mu.m thick coating of PVDC has an extremely low permeability to water vapor of 0.5 to 2 g/(m.sup.2 .times.24 h) and also an extremely low permeability to oxygen of 2.5 to 4 cm.sup.3 /(m.sup.2 .times.24 h.times.bar) (each time measured in accordance with DIN 53,122, using samples having a surface area of 5 cm.sup.2). The weight loss of cooked sausages surrounded by the casings of fiber-reinforced cellulose with internal PVDC barrier layers is about 0.5 to 1.5% per week (storage in a cold chamber at 7.degree. C., 65% relative humidity, sausage diameter 60 mm).
Casings of this type exhibit the disadvantage that due to their PVDC content problems may arise in connection with waste disposal, i.e., the disposal of the peeled-off casings. Particularly problematic is the formation of HCl and organic chlorine compounds during combustion of the casings. For example, if the weight of the PVDC coating is about 10 g per m.sup.2 of casing material, the amount of organically-bound chlorine present is about 60 g per kg of casing material.